1. Technical Field
The present invention relates to a piezoelectric oscillator, and a sensor and a multi-sensor that employ a piezoelectric oscillator.
2. Related Art
In recent years, as accompanied with miniaturization of electronic devices, miniaturization of piezoelectric oscillators such as a crystal oscillator mounted on electronic devices has been increasingly required.
In order to meet such requirement, JP-A-10-75120, as a first example, discloses a crystal oscillator that stores a crystal vibrator and an electronic component constituting an oscillation circuit in one container.
In addition, miniaturization of sensors employing a piezoelectric oscillator has been required. For the miniaturization thereof, JP-A-2004-264255, as a second example, discloses a mass measuring chip in which a piezoelectric resonator element and an IC chip are bonded to one flat plate in an electrically connecting fashion to each other. The mass measuring chip detects a specific substance adsorbed by the piezoelectric resonator element in accordance with an amount of the frequency change.
However, in the crystal oscillator (hereinafter, referred to as a piezoelectric oscillator) disclosed in the first example, even though the crystal vibrator (hereinafter, referred to as a piezoelectric substrate) and the electronic component constituting the oscillation circuit are stored in one container (hereinafter, referred to as a package), the piezoelectric substrate and the electronic component are stored in separate cavities within the package. That is, in this structure, the package needs a space for storing the piezoelectric substrate and a space for storing the electronic component separately therein, making the further miniaturization difficult.
Further, since the electronic component is a discrete component and is provided in a great number, the number of manufacturing steps increases to degrade the productivity. In addition, since the discrete component is commonly thick, it is hard to thin the crystal oscillator.
Furthermore, a circuit pattern for wiring a plurality of discrete components becomes complex so as to generate electromagnetic coupling between circuit patterns, deteriorating the performance of the oscillator disadvantageously.
The mass measuring chip (hereinafter, referred to as a sensor) disclosed in the second example has such structure that the piezoelectric resonator element and the IC chip constituting the oscillation circuit are bonded separately to the flat plate, so that the structure hardly satisfies suitable manufacturing efficiency. In addition, the sensor mounts the piezoelectric resonator element on the flat plate, being hard to be thinned.